1. Field
The present invention generally relates to sensing cables, and more particularly, to sensing cables which detect external pressure and strain.
2. Description of the Related Art
In recent years optical fibers have been used for sensing the distribution of temperature in oil and gas downhole and logging cables. Temperature sensing using distributed temperature sensing with optical fiber is a well mown technology. Generally in this system, a cable containing an optical fiber encased in a stainless steel tube (SST) is used. In this cable structure, the optical fiber is protected by the SST from external pressures and strain. Using optical fibers for measuring external pressure and strain is desired by the oil and gas industry for both downhole and logging applications. Brillouin Optical Time Domain Reflectometry (BOTDR) analyzing systems for sensing temperature and pressure distribution at the same time is under development. However, detecting external pressure and strain are both extremely difficult due to inaccuracies and dependability of the cable structure and/or fiber.
This disclosure illustrates new cable designs that address these concerns, but the invention is not limited to these specific applications, nor is the invention required to address any of these concerns.